[Squidman]

That was the one thing that I thought too. But since he claims that the water level stays low in the built-in overflow, even that wouldn't make sense. There is no way the tank could overflow without the built-in overflow filling up first. Unless the guy made some modification, like capping the overflow, which is preventing it from filling up. Even then topping off in the sump should have no effect on water level in the tank. The sump could overflow, but not the tank. Of course if he capped it AND the sump is above the tank...